Carbon-carbon brake discs are widely used on commercial and military aircraft. Wide-bodied commercial jets required improved brake materials because traditional steel brake systems simply could not absorb all of the thermal energy created during stops associated with landings. Carbon-based composites were developed which provide heat capacity, thermal conductivity, and thermal strength able to meet the demanding conditions involved in landing large commercial jets. On the military side, the lower weights as well as the thermal and strength properties of the carbon composites has helped to ensure their acceptance in brake applications.
The use of carbon-carbon composite brake discs in aircraft brakes, which have been referred to as carbon brakes, is well known in the aerospace industry. Carbon-carbon composite brake discs are manufactured by aircraft wheel and brake manufacturers using a variety of manufacturing methods, which generally require lengthy fabrication and densification methods. In recent years, aircraft manufacturers have increasingly specified the use of such carbon-carbon composite brake discs for brakes designed for use with new aircraft models. In some instances, for example in the reuse of worn carbon-carbon composite discs, it is desirable to combine or attach two or more carbon-carbon friction materials together. Typically, this is accomplished through mechanical fasteners, such as, for example, through the use of rivets.
In at least one instance, the carbon-carbon composites are alternatively held together through the use of a spot-applied molten braze material such as a Zirconium metal. To accomplish this, the carbon composites are subjected to an electrical current such that the resistance in the carbon material causes a temperature increase. A thin layer of braze material, such as a thin metal foil, is melted in the general area of the applied current. The metal melts, and after removal from the electrical current, solidifies again to locally bond the carbon-carbon composites. The finished brazed material, however, is subject to failure at a relatively low temperature, as the metal material need only melt to release the bond. Additionally, the composites are subject to oxidation, as the metal utilized is typically very reactive.
Accordingly, it may be desirable to provide an apparatus capable of bonding carbon-based composites without the need for mechanical fasteners, and without use of a molten metal material.